Partial

Use ft.Partial to make properties of an object optional.

You might also make use of the closely related utilities:

• ft.Omit
• ft.Pick

These utilities can be applied to any object codec, including one constructed by intersecting together several other object codecs.

import * as ft from "funtypes";

const UserCodec = ft.Object({
  id: ft.Number,
  name: ft.String,
});
// => Codec<{ id: number; name: string }>

const PartialUserCodec = ft.Partial(UserCodec);
// => Codec<{ id?: number; name?: string }>

type PartialUser = ft.Static<
  typeof PartialUserCodec
>;
// => { id?: number; name?: string }

assert.deepEqual(
  ft.showType(PartialUserCodec),
  "{ id?: number; name?: string }",
);

// ✅ Valid object with some keys
assert.deepEqual(
  PartialUserCodec.parse({
    name: "Forbes Lindesay",
  }),
  {
    name: "Forbes Lindesay",
  },
);

// ✅ Valid object with all the keys
assert.deepEqual(
  PartialUserCodec.parse({
    id: 1,
    name: "Forbes Lindesay",
  }),
  {
    id: 1,
    name: "Forbes Lindesay",
  },
);

// ✅ Valid object with no keys
assert.deepEqual(PartialUserCodec.parse({}), {});

// 🚨 Invalid: id should be a number or undefined
assert.throws(() => {
  PartialUserCodec.parse({
    id: "42",
    name: "Forbes Lindesay",
  });
});

It also works on objects that were wrapped in ft.Named, and will preserve the name given to the type:

import * as ft from "funtypes";

const UserCodec = ft.Named(
  "User",
  ft.Object({
    id: ft.Number,
    name: ft.String,
  }),
);
// => Codec<{ id: number; name: string }>

const PartialUserCodec = ft.Partial(UserCodec);
// => Codec<{ id?: number; name?: string }>

type PartialUser = ft.Static<
  typeof PartialUserCodec
>;
// => { id?: number; name?: string }

assert.deepEqual(
  ft.showType(PartialUserCodec),
  "Partial<User>",
);